beforeEach(() => {
  window['__zone_symbol__FakeAsyncTestMacroTask'] = [
    {
      source: 'HTMLCanvasElement.toBlob',
      callbackArgs: [{ size: 200 }]
    }
  ];
});
 
it('toBlob should be able to run in fakeAsync', fakeAsync(() => {
    const canvas: HTMLCanvasElement = document.getElementById('canvas') as HTMLCanvasElement;
    let blob = null;
    canvas.toBlob(function(b) {
      blob = b;
    });
    tick();
    expect(blob.size).toBe(200);
  })
);